Easy SUDOKU 4x4,6x6,7x7 with Secret Tools

Easy SUDOKU 4x4,6x6,7x7 with Secret Tools
Do you want to strengthen your kid's thinking ability?
Why don't you train your kids' head by doing puzzles with some Doraemon's secret tools?
That is the origin of the development of this application.
I hope children would have fun playing with SUDOKU, train the brain, and acquire thinking skills.
It also becomes a brain train of elderly people.
There are 100 levels in each puzzle, so start with the one you can do easily.
Since Sudoku puzzles are generated automatically, you can play with infinite number of Sudoku puzzles!
You can also play 4x4,6x6,7x7,8x8 ordinary number sudoku.
Sudoku Rules
Put all four 1,2,3,4 (or1,2,3,4,5,6,7) numbers in 4(or 6,7) vertical columns, 4(or 6,7) horizontal rows, 4(or 6,7) squares surrounded by bold lines.
Step into the world of numerical puzzles!